Balloon catheters are conventionally used in a wide variety of medical procedures. For example, a balloon is inflated during percutaneous transluminal coronary angioplasty (PTCA) to dilate a stenotic blood vessel and may also be used to deliver a stent to support the vessel lumen in an open position. In addition, the distal end of a guidewire is sometimes equipped with at least one inflatable balloon to provide temporary occlusion of a vessel or to anchor the guidewire within a vessel. An occlusion guidewire can be used to prevent debris generated during vessel treatment from moving with the flowing blood to embolize distally. Anchoring the guidewire helps to prevent the guidewire from being displaced from its position while treatment catheters are advanced or withdrawn over the placed guidewire.
Typically, balloon inflation is accomplished by injecting a liquid under pressure into an inflation lumen of a balloon catheter. However, before the catheter is used, air must be purged from the inflation lumen and the balloon itself to eliminate the risk of an air embolism entering a vessel if the system were to leak or the balloon were to rupture. The air also must be evacuated from the balloon to accomplish a desired inflation of the balloon using a specific volume of liquid without the need to account for compression of an unknown volume of air within the balloon.
A common method of purging a balloon catheter prior to use involves connecting a syringe to the proximal end of the inflation lumen and drawing out as much air as possible. Liquid is then injected into the catheter while the balloon is held vertically to allow the remaining air within the catheter to rise through the inflation liquid towards an inflation port. Liquid and some air bubbles are withdrawn from the catheter, and liquid is again injected. These steps may have to be repeated multiple times to adequately purge the catheter, requiring a substantial amount of preparation time. Therefore, it would be desirable to provide a balloon catheter that overcomes the aforementioned and other disadvantages.